1. Field of the Invention
The present invention relates to a transmissive color liquid crystal display utilizing the color field sequential method.
2. Prior Art
FIG. 18 is a cross sectional view of a backlight used in a conventional transmissive liquid crystal display disclosed in JP-A-8-122534. In FIG. 18, numeral 101 designates a backlight 101 including a light-guiding plate 102, a reflection layer 103 disposed on the rear surface of the light-guiding plate 102, a diffusion layer 104 disposed on the front surface of the light-guiding plate 102, a linear light source 105 disposed in the vicinity of a side edge of the light-guiding plate 102, and a reflector 106 surrounding the linear light source 105. Numeral 107 designates an open side edge of the light-guiding plate 102 opposite to the linear light source 105. The open side edge 107 is exposed and closed by a shutter plate 108 arranged pivotally about an axis 108a. On a surface of the shutter plate 108, which may face to the open side edge 107, a reflection film 109 is disposed.
Next, an operation of the backlight 101 will be described. The shutter plate 108 is opened so as to expose the open side edge 107 in the use of the liquid crystal display in the situation where environmental illumination is sufficient, for example, the outdoors. The rays from the linear light source 105, which will be referred to as internal rays hereinafter, enter light-guiding plate 102 directly from the linear light source 105 or indirectly after reflection on the reflector 106. While some fractions of internal rays leak out from open side edge 107, external rays including the rays of the sun enter the light-guiding plate 102 through the open side edge 107, and the incoming external rays are in excess of internal rays outgoing through the open side edge 107. Some fractions of internal and external rays in the light-guiding plate 102 reflect at the reflection layer 103 so as to be oriented frontward. Internal and external rays in the light-guiding plate 102 finally outgoes from the backlight 101 uniformly along the direction indicated by arrow A while the rays are diffused by the diffusion layer 104.
The shutter plate 108 is closed so as to cover the open side edge 107 in the use of the liquid crystal display when environmental illumination is insufficient, for example, in a house since external rays entering through the open side edge 107 are less than internal rays outgoing through the open side edge 107 if shutter plate 108 is open. Only internal rays from the reflector 106 enter light-guiding plate 102 directly from the linear light source 105 or indirectly after reflection on the reflector 106. Some fractions of internal rays reflect on the reflection film 109 and return into the light-guiding plate 102. Some fractions of internal rays in the light-guiding plate 102 reflect at the reflection layer 103 so as to be oriented frontward. Internal rays in the light-guiding plate 102 finally outgoes from the backlight 101 uniformly along the direction indicated by arrow A while the rays are diffused by the diffusion layer 104.
JP-A-8-122534 also discloses a modified backlight comprises a special reflection mirror at the open side edge 107. The reflection mirror has a transmittance property that varies depending upon angles of incidence of rays, whereby the mirror reflects rays inside the light-guiding plate 102, but admits external rays to the light-guiding plate 102.
JP-A-8-122534 discloses another modified backlight comprises a detector for detecting the illumination of external rays, and drive means, e.g., a motor, for opening and closing the open side edge 107 automatically in response to the environmental illumination.
FIG. 19 is a cross sectional view of another conventional transmissive liquid crystal display disclosed in JP-A-10-68948. In FIG. 19, numeral 201 designates a transmissive liquid crystal display including a liquid crystal display panel assembly 202, a fenestra 203 formed in the housing (not shown) of the liquid crystal display and disposed in the vicinity of the liquid crystal display panel assembly 202, a first light-guiding path 204 arranged behind the liquid crystal display panel assembly 202, a lamp unit 205 disposed in the vicinity of the side end of the first light-guiding path 204, and a second light-guiding path 206 for guiding external rays passing through the fenestra 203 to the first light-guiding path 204. Numeral 207 identifies a shutter plate for opening and closing the fenestra 203. A diffusion layer 208 is disposed on the rear surface of the first light-guiding path 204. Low-reflectance films 209 cover the front surface of the liquid crystal display panel assembly 202 and the fenestra 203, respectively. Reflection films 210 are disposed on the internal walls of the second light-guiding path 206 and on the internal wall of the shutter plate 207, respectively.
Next, an operation of the transmissive liquid crystal display 201 will be described. The lamp unit 205 is turned off and the shutter plate 207 is opened so as to expose the fenestra 203 in the use of the liquid crystal display when the environment is sufficiently bright. In this case, external rays including the rays of the sun enter the second light-guiding path 206 through the fenestra 203. While some fractions of external rays reflect on the reflection film 210 on the inner walls of the second light-guiding path 206, external rays reach the first light-guiding path 204. Then, the back surface of the liquid crystal display panel assembly 202 is irradiated with external rays uniformly while the diffusion layer 208 diffuses external rays.
On the contrary, the lamp unit 205 is turned on when the environmental illumination is insufficient. Accordingly, the rays from the lamp unit 205, which will be referred to as internal rays hereinafter, enters first light-guiding path 204. In addition, the shutter plate 207 is shut to close the fenestra 203 since the illumination required for irradiating the liquid crystal cannot be ensured if internal rays quit through the second light-guiding path 206 and the fenestra 203. Another reason for closing the shutter plate 207 is for protecting unanticipated external rays from the fenestra 203 that may directly come into human eyeshot, causing difficulty to watch the display panel. By the closed arrangement, internal rays that have entered the second light-guiding path 206 reflect on the reflection film 210 on the shutter plate 207 to return to the second light-guiding path 206, reflect on the reflection film 210 on the inner wall of the second light-guiding path 206, and enter the first light-guiding path 204, again. Internal rays that have entered the first light-guiding path 204 are diffused by the diffusion layer 208 and shine up the reverse side of the liquid crystal display panel assembly 202 uniformly.
JP-A-10-68948 also discloses a modified structure comprising a light-collecting element for collecting external rays, an optical fiber for guiding external rays collected by the light-collecting element to the fenestra 203, and a coupling element for coupling the optical fiber with the fenestra 203.
The conventional transmissive liquid crystal display shown in FIG. 18 has a drawback that primary color components, e.g., R (red), G (green), and B (blue) cannot be extracted from external rays admitted through the open side edge 107. Therefore, when external rays are employed, full color images are not presented on the liquid crystal display panel assembly without provision of color filters.
In addition, the conventional transmissive liquid crystal display shown in FIG. 18 has another drawback that it is not easy to control the entrance of external rays and the leak of the internal ray since the control of the entrance of external rays and the leak of the internal ray is achieved by adjusting the shutter plate 108.
Similarly, the transmissive liquid crystal display shown in FIG. 19 has a drawback that primary color components, e.g., R, G, and B cannot be extracted from external rays that have passed through the fenestra 203. Therefore, when external rays are employed, full color images are not presented on the liquid crystal display panel assembly without provision of color filters.
In addition, the conventional transmissive liquid crystal display shown in FIG. 19 has another drawback that it is not easy to control the entrance of external rays and the leak of the internal ray since the control of the entrance of external rays and the leak of the internal ray is achieved by adjusting the shutter plate 207.
It is therefore an object of the present invention to provide a transmissive color liquid crystal display that can present color images using external rays and can readily control the entrance of external rays and the leak of the internal ray.
In accordance with an aspect of the present invention, a transmissive color liquid crystal display includes a first liquid crystal section, a light-guiding element, a second liquid crystal section, and first and second liquid crystal drivers. The first liquid crystal section presents color images. The light-guiding element is situated behind the first liquid crystal section for orienting rays toward the first liquid crystal display section. The second liquid crystal section includes a plurality of zones capable of transmitting wavelength bands of external rays, respectively, the zones may be selectively activated for introducing colored external rays through respective zones to the light-guiding element. The first liquid crystal driver controls the first liquid crystal section. While color-component data extracted from full color image data is input into the first liquid crystal driver in a time-division manner, the first liquid crystal driver activates and deactivates pixels on the first liquid crystal section for presenting images on the first liquid crystal display section on the basis of the color-component data in time division manner. The second liquid crystal driver selectively activates the zones in the second liquid crystal section in time division manner for introducing colored external rays of which wavelength bands correspond to the color-component data through the zone to the light-guiding element for irradiating the images on the first liquid crystal section with the colored external rays in time division manner.
With such a structure, the second liquid crystal section is used for changing the color of introduced external rays, thereby changing the color of the image on the first liquid crystal section sequentially. Therefore, color images can be presented on an image display section of a liquid crystal display panel without provision of color filters using external rays.
In an embodiment, the first and second liquid crystal sections may be parts of a single liquid crystal display panel assembly. The zones of the second liquid crystal sections may be respectively provided with color filters capable of selectively transmitting color components of external rays, each of the color components having a wavelength band corresponding to the color-component data. Thus, one of the color components are admitted through one of the zones and one of the color filters on the zone when the zone is activated by the second liquid crystal driver.
With such a structure, by virtue of the color filters on the second liquid crystal section, rays exhibiting color components, each having a wavelength band corresponding to the color-component data, can be obtained readily from external rays.
In another embodiment, the transmissive color liquid crystal display may further comprise a prism for dispersing external rays into visible spectrum exhibiting color components. The spectrum resulting from external rays by the prism may strike the second liquid crystal section, whereby one of the color components are admitted through one of the zones of the second liquid crystal section when the zone is activated by the second liquid crystal driver.
With such a structure, by virtue of the prism, rays exhibiting color components, each having a wavelength band corresponding to the color-component data, can be obtained readily from external rays.
The transmissive color liquid crystal display may further comprise a slit plate facing to the second liquid crystal section. The slit plate may be provided with a plurality of apertures of which the positions respectively correspond to the zones of the second liquid crystal section, whereby one of the color components are admitted through one of the apertures and one of the zones of the second liquid crystal section when the zone is activated by the second liquid crystal driver.
With such a structure, since the positions of the narrow apertures correspond to the wavelength bands of external rays admitted to the light-guiding element, the wavelength bands are narrower so that clear color images may be presented and the resultant full color image may exhibit an improved reality. In addition, the design can be changed easily for matching the wavelength bands with various sorts of color component data.
The transmissive color liquid crystal display may further comprise a third liquid crystal section activated for introducing external rays through the third liquid crystal section to the prism, and a third liquid crystal driver for controlling the third liquid crystal section. The first and third liquid crystal sections may be parts of a single liquid crystal display panel assembly.
With such a structure, the third liquid crystal section may be used for introduction and shutoff of external rays, so that the intensity of external rays can be controlled readily by the third liquid crystal driver.
The transmissive color liquid crystal display may further comprise a light source unit disposed near the light-guiding element. The light source unit is capable of emitting colored internal rays, of which a wavelength band corresponds to the color-component data, introduced to the light-guiding element for irradiating the images on the first liquid crystal section with the colored external rays in a time division manner.
With such a structure, color images can be presented on an image display section of a liquid crystal display panel without provision of color filters using internal rays.
The transmissive color liquid crystal display may further comprise a battery charge monitor for detecting remaining charge of a battery for driving the transmissive color liquid crystal display, and an external-ray controller for controlling to use external rays when the battery charge monitor detects that the remaining charge is less than the threshold.
With such a structure, the remaining charge of the battery may be efficiently utilized for presenting color images since external rays are controlled on the basis of the remaining charge.
In an embodiment, the transmissive color liquid crystal display may further comprise a light source unit and a half-mirror. The light source unit may be positioned at the same side of the light-guiding element as that where the second liquid crystal section is positioned. The light source unit may be disposed near the light-guiding element and may be capable of emitting colored internal rays, of which a wavelength band corresponds to the color-component data, introduced to the light-guiding element for irradiating the images on the first liquid crystal section with the colored external rays in a time division manner. The light source unit may be positioned at the same side of the light-guiding element as that where the second liquid crystal section is positioned. The half-mirror may be situated between the light-guiding element and the light source unit. The half-mirror may reflect external rays, which have passed through the second liquid crystal section, toward the light-guiding element and may transmit internal rays emitted from the light source unit toward the light-guiding element.
With such a structure, internal rays hardly leak out from the second liquid crystal section that is an intake of external rays, so that full color images are prevented from hazing.
In an embodiment, the transmissive color liquid crystal display may further comprise a light detector for measuring a sum of intensity of internal rays and external rays of each color component within the light-guiding element, and a light intensity optimizer for controlling the light source unit on the basis of the sum of the intensity measured by the light detector, so as to adjust the intensity of internal rays.
With such a structure, the sum light intensity of internal and external rays of each color component may be maintained constant although the intensity of external rays varies.
In another embodiment, the transmissive color liquid crystal display may further comprise a light detector for measuring a sum of intensity of internal rays and external rays of each color component within the light-guiding element, and a light intensity optimizer for controlling the second liquid crystal section on the basis of the sum of the intensity measured by the light detector, so as to adjust the intensity of introduced external rays.
With such a structure, the sum light intensity of internal and external rays of each color component may be maintained constant although the intensity of external rays varies.
In an embodiment, the light-guiding element may include a first light-guiding element, to which internal rays are admitted, and a second light-guiding element, to which external rays are admitted. The transmissive color liquid crystal display may further comprise a reflection film mounted on a side end surface of the first light-guiding element opposing to a side to which internal rays are admitted.
With such a structure, although some fractions of internal rays progress longitudinally through the first light-guiding element, the fractions of internal rays return to the first light-guiding element by the reflection film, whereby efficiency of internal rays may be enhanced.
The first liquid crystal section may be situated in front of the first light-guiding element while the first light-guiding element may be situated in front of the second light-guiding element.
With such a structure, efficiency of internal rays may be enhanced.
In another embodiment, the first liquid crystal section may be situated in front of the second light-guiding element while the second light-guiding element may be situated in front of the first light-guiding element.
With such a structure, efficiency of external rays may be enhanced.
In an embodiment, the transmissive color liquid crystal display may further comprise a half-mirror situated between the first light-guiding element and the second light-guiding element. The half-mirror may reflect internal rays admitted to the first light-guiding element and may transmit external rays admitted to the second light-guiding element.
With such a structure, efficiency of internal rays may be enhanced.
In another embodiment, the transmissive color liquid crystal display may further comprise a half-mirror situated between the first light-guiding element and the second light-guiding element. The half-mirror may reflect external rays admitted to the second light-guiding element and may transmit internal rays admitted to the first light-guiding element.
With such a structure, efficiency of external rays may be enhanced.
In an embodiment, the light source unit may include a plurality of linear light sources.
With such a structure, each light source can irradiate the side end surface of the light-guiding element entirely with internal rays having relatively high intensity and the light source unit can have a small thickness.
In another embodiment, the light source unit may include a plurality of point light sources.
With such a structure, the transmissive color liquid crystal display may be manufactured in a small size and be operated at a low cost.
In another embodiment, the light source unit may include a plurality of surface light sources.
With such a structure, internal rays with high brightness may be employed for presenting full color images.
In accordance with another aspect of the present invention, a transmissive color liquid crystal display includes a liquid crystal display panel assembly, a light-guiding element, a first liquid crystal driver, a second liquid crystal driver, and a color selecting mechanism. The liquid crystal display panel assembly may include an image display section for presenting color images and an external-ray transmissive section activated for introducing external rays through the external-ray transmissive section to the light-guiding element. The light-guiding element may be situated behind the image display section for orienting rays toward the image display section. The first liquid crystal driver may control the image display section. Color-component data extracted from full color image data may be input into the first liquid crystal driver in a time-division manner. The first liquid crystal driver may activate and deactivate pixels on the image display section for presenting images on the image display section on the basis of the color-component data in time division manner. The second liquid crystal driver may activate the external-ray transmissive section for introducing external rays through the external-ray transmissive section. The color selecting mechanism may select colors of external rays in time division manner for introducing colored external rays of which wavelength bands correspond to the color-component data to the light-guiding element for irradiating the images on the image display section with the colored external rays in time division manner.
With such a structure, external rays are introduced by the external-ray transmissive section that is integral with the liquid crystal display panel assembly having image display section. The color selecting mechanism is used for changing the color of introduced external rays, thereby changing the color of the image on the image display section sequentially. Therefore, color images can be presented on the image display section of the liquid crystal display panel without provision of color filters using external rays.